Hydrocarbons feedstocks are currently extracted from the ground and combusted to generate energy. These hydrocarbon feedstocks currently are favored as they are easily transported as liquid (i.e. gasoline). These non-renewable feedstocks will eventually be depleted over time. Furthermore, when combusted these materials create carbon dioxide, a greenhouse gas that may contribute to global warming. A key challenge for promoting and sustaining the vitality and growth of the energy industry (as well as the entire industrial sector of society) is to develop efficient and environmentally benign technologies for generating fuel, such as combustible hydrocarbons, from renewable resources. Notably, if hydrocarbon fuel for consumption in fuel cells (and other types of equipment) can be generated efficiently from renewable sources, then non-renewable resources such as petroleum feedstocks can be used for other, more beneficial, and less environmentally deleterious purposes. Moreover, the generation of energy from renewable resources such as biomass, reduces the net rate of production of carbon dioxide, an important greenhouse gas that contributes to global warming. This is because the biomass itself, i.e., plant material, consumes carbon dioxide during its life cycle.
A series of patents to Elliott et al. and assigned to Battelle Memorial Institute describe the production of a “product gas” (primarily methane, carbon dioxide, and hydrogen) from liquid organic material, using a metal catalyst. Specifically, U.S. Pat. No. 5,616,154 describes a process wherein the liquid organic material and water are reacted in a pressure vessel at a temperature of from about 300° C. to about 450° C., and at a pressure of at least 130 atm (1,911 psi). The catalyst used in the process is a reduced form of ruthenium, rhodium, osmium, or iridium. The liquid organic material used as a feedstock is defined as “any organic compound or mixture of such compounds that exists as or decomposes to a liquid or a gas at a temperature of at least 250° C. and at a pressure of 50 atm or more.” The process is aimed at both the production of energy and the destruction of liquid waste streams, such as hexamethylene diamine in water (a by-product from the production of nylon 6,6).
U.S. Pat. No. 5,814,112 (to Elliott et al. and a continuation-in-part of the patent described in the previous paragraph) describes a nickel/ruthenium catalyst for steam reforming and hydrogenation reactions. U.S. Pat. No. 6,235,797, also to Elliott et al., describes a ruthenium catalyst that is essentially free or nickel and rhenium and which is adhered to a titania support, wherein the titania is greater than 75% rutile. The catalyst is specifically designed for use in the aqueous-phase hydrogenation of organic compounds.
In similar fashion, U.S. Pat. No. 5,630,854, issued to Sealock et al. and assigned to Battelle Memorial Institute, describes a method of converting waste organic materials into a product gas. In this method, the stream of organic waste is reacted in a pressure vessel that has been purged of oxygen. The reaction takes place at elevated temperatures and at a pressure of at least 50 atm (735 psi), in the presence of a reduced nickel catalyst.
U.S. Pat. No. 4,300,009, to Haag et al., describes a process for manufacturing liquid hydrocarbons. In this process, organic plant material having a hydrogen-to-carbon ratio of from about 1 to 1, to about 2.2 to 1, is contacted at elevated temperature and pressure with a crystalline aluminosilicate zeolite having a pore diameter great than about 5 Å. According to the specification, at least 50% of the liquid hydrocarbons so produced distill at a temperature below about 170° C.
U.S. Pat. Nos. 4,503,278 and 4,549,031, both issued to Chen & Koenig, describe a method for converting carbohydrates to hydrocarbons. In this process, aqueous solutions of the carbohydrate are contacted with a particular type of crystalline silicate zeolite catalyst at elevated temperatures and at pressures ranging from 1 to 50 atm, thereby yielding hydrocarbon products. A similar approach is described in a paper authored by Chen, Koenig and Degnan Jr. (August 1986) “Liquid Fuel from Carbohydrates,” Chemtech 506-509.
U.S. Pat. No. 5,516,960, to Robinson, describes a method for producing hydrocarbon fuels wherein polyhydric alcohols, cellulose, or hemicellulose are reacted to yield hydrocarbons. In this reaction, when using cellulose or hemicellulose as the feedstock, the cellulose or hemicellulose is first depolymerized to sorbitol or xylitol, respectively. This is accomplished using well known reductive depolymerization chemistry. The sorbitol or xylitol is then converted to iodoalkanes by a reacting the sorbitol/xylitol with hydroiodic acid and a liquid-phase, phosphorous-containing reducing agent. This reaction yields primarily 2-iodohexane in the case of sorbitol and 2-iodopentane in the case of xylitol. The reaction takes place in boiling aqueous solution at atmospheric pressure. The iodoalkanes so formed may then be de-halogenated to yield alkenes, and then reduced to yield alkanes.
Yoshida & Matsumura (2001) “Gasification of Cellulose, Xylan, and Lignin Mixtures in Supercritical Water,” Ind. Eng. Chem. Res. 40:5469-5474, describe reacting cellulose, xylan, and lignin mixtures in supercritical water in the presence of a nickel catalyst. The reactions were carried in a sealed vessel purged of oxygen, at a temperature of 400° C., and at a pressure of from 26 to 29 MPa (3,770 to 4,205 psi).
Elliott et al. (1999) “Chemical Processing in High-Pressure Aqueous Environments. 6. Demonstration of Catalytic Gasification for Chemical Manufacturing Wastewater Cleanup in Industrial Plant,” Ind. Eng Chem. Res. 38:879-883, describes the high-pressure (˜20 MPa) catalytic gasification of organic compounds as a possible route for purifying wastewaters generated at chemical manufacturing plants. The equipment used was a fixed-bed, tubular reactor and was operated at 20 MPa and 350° C.
Nelson et al. (1984) “Application of Direct Thermal Liquefaction for the Conversion of Cellulosic Biomass,” Ind. Eng. Chem. Prod. Res. Dev. 23(3):471-475, describes the chemical conversion of pure cellulose into a mixture of phenol, cyclopentanones, and hydroquinones. The conversion was accomplished by charging an autoclave with cellulose, water, and anhydrous sodium carbonate. The autoclave was then purged of air. The reaction was then initiated at temperatures of from 250° C. to 400° C., at pressures ranging from roughly 10.3 MPa (1,494 psi) to 20.7 MPa (3,000 psi).
Thus, there remains a long-felt and unmet need to develop methods for producing hydrocarbons from renewable resources such as biomass. Such methods would convert either low value waste biomass such as sawdust and cheese whey or biomass created for energy production such as switchgrass to hydrocarbons. The combustion of the resulting hydrocarbons would not add to the net production of carbon dioxide (a greenhouse gas) as the resulting carbon dioxide will be refix through biomass growth. The resulting hydrocarbon would have a low sulfur content, would be renewable, and derived from non-flammable starting materials. Moreover, to maximize energy output, there remains an acute need to develop a method for producing hydrocarbons that proceeds at a significantly lower temperature than catalytic cracking of hydrocarbons derived from petroleum feedstocks. Lastly, there remains a long-felt and unmet need to simplify the reforming process by developing a method for producing hydrocarbons that can be performed in a single reactor.